Shock absorber



Fehzs, 1939. WQPECK- 2,148,497

' SHOCK ABSORBER F'iled Nov. 10, 1937 Patentedlfeb. 2e, 1939 r 148,497'I UNITED STATES PATENT OFFICE l snoer; ABSORBER y william c. Peek,Washington, n. C. Application November 10, 1937, Serial No. 173,843 eclaims. (o1, iss-ss) (Granted under the act of Maren 3, 1883, as'

amended April so, 192s; 37o o. o. 757) The invention described hereinmay be manu- With the above and other objects in view, the factured andused by or for the Government for 'invention consists-in the novelconstruction, comgovernmental purposes, without the payment to bination,and arrangement of parts hereinafter me of any royalty thereon. morefully described with reference to the accom- 5 The general design of thepresent conventional panying drawing, wherein: y hydraulicshock-@absorbers is such that but one Figurel is a longitudinalsectional view of a condition of operation may be considered in theshock absorber embodying theA invention and basic design. v The Workingrequirements usually shown in completely extended condition; selectedfor the basis 'are the most severe ex- Figure 2 is asimilar sectionallview of the shock l pected. leaving the requirements between the leastabsorber in a state of partial collapse; the meter- 10 and the mostsevere Without adequatevconsideraing -pin being in the same relativeposition with tion in the design. respect to the plunger head as shownin Figure l,

The operation of the conventional shock-abf and l sorber strut on avehicular or an airplane chassis Figure 3 is a detail sectional viewillustrating l is also partially dependent upon the unsprung` a changein the relative position of the meterin 15 weight and geometricarrangements of the chaspin with respect to the plunger head. sis-andthe characteristics of the tire used. This The'herein described shockabsorber strut confurther limits the satisfactory action of the consistsessentially of a mainl cylinder IIJ adapted to ventional shock-absorberto the type of chassis contain an incompressible fluid medium, such asand tire considered in the basis of design. 'oil; a spring-loadedsmaller cylinder I Ii slidable in 20 Recognition of\the need forashock-absorbing the main cylinder and constituting a pston'or strut,whoseoperation would approach the criplunger; and a metering pin I2. Thecylinder III terion ofv offering a constant retarding force is closed atits outer or bottom end by an end throughout its'cntraction stroke whensubjected fitting I3 and is providedat its inner or upper to a varietyof operating conditions, has lead to. end with a packing box I4 andpacking gland ring 2'5 the conceptibnof the hereinafter described hynutI5. The cylinder I0 is adapted to be attached draulic shock-absorber. toan airplane landing gear chassis by'suitable l Hence, the primary objectoi the present invenmeans such as a clevis I 6 forming an integral ttionis to provide a shockabsorbing mechanism part ofthe cylinder-endtting I3. 'I'he piston II4 that will (1) absorb energy and while sodoing has its lower end or head I1 provided with a leak 30 transmit asensibly constant retarding force to orice I8 through which when thepiston is forced the structureonwhich it is mounted, (2) absorb into thecylinder the oil passes into the piston impacts and while so doingtransmit a minimum chamber I9, the latter being closed at its upper endforce to the structure on, which it is mounted, and by a wall 20 formingan integral part 0f the piston 3;, v(3) ofl'er a retarding force whosemagnitude is a and spaced inwardly '0f the piston-end fitting 2|. 35function ofthe rate ofthe relative motion between The fitting 2l isprovided with suitable means. -the piston and the cylinder of-the-'shock absorber, such as a clevis 22, for attachment to an airplane-Anoche-,r"objector the invention is t0 provide main structure -orfuselage and is asliding t in a shockabsorber mechanism the operationofi the piston. It is prevented from being -forced y 4f, which wu).independent ofthe effects of the un- Out 0f the piston by means ofairing nut 23 40 sprung ma thg'ghagsis on which if, ismounted, screwedon the end ofthe piston and engaging (2) vsensibly independent 0f .theeffects'of the over a shoulder on the fitting. A set of springscharacteristics of the tireused with the chassis on 24 is chamberedunder an initial compressive load which the shockebsorber'is mounted;and 3) in the piston between the piston-end fitting 2| .45 readily adjusable so thatregulation ofthe magand the piston restraining wall 20. Thepiston nitude'of the retarding force may easily be made. I liloatsbetween the iluid in the cylinder II) and A further object of Jtheinvention is td provide the set of springs 24. AThe metering pin, I2 isa shock-absorbing mechanism in the design of rigidly secured at one end25 t0 the pistonfend whlch'the complete range of working conditionsfltting 2| and extends dOWnWardlY intO thevDiS- 5b may be given-equalconsideration. ton II, through the journal 26 of the piston re- 50 Astill vfurther object ofthe'invention is t'o prostraining wall 20, withits free end 21 terminating vide a shock-absorbing mechanism that willbe in the piston-'head orifice I8. The mechanical readilyinterchangeable-and function efllcentconnection between the piston IIand the meterlyondlilerenii types 0f aircraft or vehicles. of in'g pinI2 is such that their motion relative to sensibly the same weight; thecylinder Il! is sensibly as one uniti Relative 5I 'motion between themetering-*pin and the piston is, however. possible but is restricted bymeans of the springs 24. The free end 2'I yof the metering pin is shaped(tapered) so that relative motion between the pin and the piston causesa change in the enective area ofthe piston-head orifice IB,

- resists closure.

as will be'noted from a and Figure 3.

The relative. position ofthe metering pin I2 with respectto the plungerhead I1Aisfa function comparison of Figure 1 of the degree ofcompression of :the internal springs 24 in the upper end of the lpistonor plunger. The compression of these springs is a function of the forcewith which the strut resists closure: hence, the relative position ofIthe metering pin is a function of the load tending-to collapse thestrut. Regulation of the initial-compressive load on the springs 24, theshape (taper) oi' the free end 21 -of the metering pin, and the sire ofthe orifice I8 in the piston head will control the action of theshock-absorbing mechanism under various rates of closure (rates ofrelative motion between the cylinder II! and the piston l I) of theshock absorber.

Operation of the shock absorber: The cylinder Il is filled with oil tosuch a height that, with the shock absorber completely extended, thepiston head I1 is submerged. When closure of the shock absorber occurs,the oil is forced from the cylinder through the piston-head orifice I8into the piston II and the orifice characteristics determine the forcewith which the shock absorber When this resisting force(approximatelyequal'to the force causing closure of the shock absorber)exceeds the initial compressive loads on the springs 24, relative motionbe. tween themetering pin I2 andthe piston II oc-` curs. This relativemotion changes the effectiveoriflce characteristics and results in achangein the force resisting closure. The directionpf thisv change inresisting force and magnitude can 'be controlled in the design of theshock absorber. When the force causing closure falls below the initialcompressive force on the springs 2l, thel metering pin and the pistonreturn to their initialrelative position illustrated in Figures 1 and 2.

. In this position, the eective orifice characteristics are such thatthe shock absorber will effectively snub any tendency to cause rebound.

From the foregoing it will be seen that the invention provides a novelconstruction and design of shock absorber that will allow considerationoi' the entire working range of requirements and will eliminate to alarge degree the influence of `the chassis and the tire characteristicson the operation of the shock absorbing mechanism. Thus, with thisimproved type of shock absorber it will be possible to provide moreefficient shockabsorption inthe range usually encountered as well asmeeting the requirements of the severest conditions. Also, this shockabsorber will allow the use of various types of chassis and tireswithout influence on its design..

It is to be understood that the above description and the accompanyingdrawing correspond onlyto the general and preferred embodiment of theinvention and that various changes in construction, proportion, andarrangements of parts may be made within the scope of the appendedclaims.

' Having thus described the invention, I claim:

1. A shock absorber comprising a cylinder, a hollow piston slidable inthe cylinder and having .an orifice in -the head thereof, a piston-endfitting slidable in the said hollow piston, a set of springschamberedunder an initial compressive'load between the piston and the piston-endfitting, a

metering pin rigidly secured-at one end to the piston-endfitting andextending into the piston with its free end terminating in "thepiston-head orifice, and means for connecting the said cylinder and thesaid piston-end fitting respectively -to 4the parts whose movements areto be cushioned.

2. A shock absorber. comprising a main cylinder; asmaller cylinderslidable in the main cylinder-and having an orice inthe head thereof, a

shouldered cylinder-end fitting slidable in the smaller cylinder,A aring nut screwed on the end of the pisto and engaged over the shoulderVof the ring nut, cylinderfclosing means forming an integral part ofthesmaller cylinder and closing Ithe outer. end of the latter ininwardlyspaced relation'to the cylinder-end fitting, a set olf springschambered under an initial compressive load in the space between thecylinder-end fitting and the cylinder`- closing means, a metering pinrigidly secured at one end to the cylinder-end fitting and extendinginto the smaller cylinder' with i-ts free end cooperating with the 'saidorifice,

and means for connecting the'said. main cylinder and the saidend-fitting of the smaller cylinder respectively to the par-tswhose'movements are to be cushioned.

3. A shock absorber comprising a cylinder, a piston slidable in thecylinder and having an orifice in the head thereof, a piston-end ttingslidable in the piston, a metering pin carried by yand loosely coupledto the said member for limited sliding movement upwardly and downwardlywith respect thereto, said piston having an orice, an elastic body incompression between the member and the-piston for yieldably holding the'piston at the limit of its downward movement relative to the member andfor transmitting to the said member the force resisting inward motion ofthe piston into the cylinder, and a metering pin carried by the saidmember and cooperating with the orifice of the piston to substantiallyreduce the effective orifice area when the piston is at the limit of itsdownward movement relative to vthe memberl and to progressively increasethe effective orifice area during the entire upward movement of thepistongrelative to the member.

5.- A shock absorber comprising a cylinder adapted to contain a liquidand having means of attachment'to a part to be cushioned, a memberhaving means of attachment to \another part to be cushioned, a piston slidablev in the cylinder and loosely coupled to the said member forlimited movement upwardly and downwardly with respect thereto, saidpiston having an orifice, spring means chambered between the member -andthe piston and providing a spring force eifective to position and tohold the piston at the limit of its downward movement relative to themember whenever -the force causing closure of the Shockabsorber is lessthan the said spring force, and a metering pin fixed to the said memberand cooperating with the orifice of the piston to substantially reducethe effective area of the said o ce when the piston is positioned atVthe limit o its downward movement relative to the member and toprogressively increase the effective .area of the oriice during theupward movement ofthe piston relative to the member.

6. A shock absorber comprising a cylinder adapted to contain a body ofliquid, and having meansof attachment to a part to be cushioned. apiston slidable in the cylinder fand having two non-communicatingchambers i serving as a spring-receiving chamber and a liquid-receivingchamber respectively, the said latter chamber having an orifice topermit the ow of liquid into and out of the said chamber. a memberhaving means of attachment to another part to be cush- `piston relativeto the said member;

ioned and extending intothe said spring cham-` ber, said piston and saidmember being interconnected to have. limited relative movement towardand away from each other, spring means arranged in the spring chamber toprovide a spring load between the piston and the member eiective tomaintain the latter at the limit of their relative movement away fromeach other whenever thel `force causing closure of the shock absorber isless' than the said spring load, and a metering pin ixed to said memberand cooperating with the orice of the liquid chamber to change theeffective are'a of the orifice upon motion of the said WILIIAMGPECK.

